Method for fluid carriage in deep-seam coal hydraulic mining

ABSTRACT

The present invention relates to a method for fluid carriage in deep-seam coal hydraulic mining, aimed at the mining of coal seams buried underground at depths of 500 metres to below several thousands of metres. By means of methods such as well drilling and tubular columns, hydraulic power is conveyed to the coal seam excavation using tubular columns, to erode and cut coal buried underground, and by circulating fluid at a certain flow rate, cut coal is carried to the surface, achieving unmanned excavation in the shaft. The present method is an integrated coal exploitation technique achieving synchronous mining of coal field gas and solids, and is suitable for coal seams where conventional methods are unable to mine or mining is not economically viable, while also being suitable for establishing gasification channels for underground coal gasification.

TECHNICAL FIELD

Embodiment of the present invention relates to a novel process forhydraulic mining and fluid carrying of deep-seam coal, mainly aiming atmining of coal seams buried in the ground under 500 meters to thousandsof meters of depth.

BACKGROUND

It is in developing that by processes such as well drilling, tubularcolumns and the like, coal deeply buried in the ground is washed andcut, and the cut coal is brought out of the ground through thecirculation of fluid. The tubular columns are utilized to transmithydraulic power to the coal seams for tunneling and then transmit coalto the ground through fluid, realizing downhole unmanned tunneling.

SUMMARY

The novel process is a coal development technology for realizing theintegration of synchronous mining of gas and solid of coal fields, isespecially suitable for the coal seams which can not be mined with aconventional method or are uneconomically mined, and is suitable forestablishment of gasification tunnels of underground gasification ofcoal.

To overcome the deficiencies of the prior art, embodiment of the presentinvention provides a novel process for hydraulic mining and fluidcarrying of deep-seam coal, particularly a method for hydraulic miningand fluid carrying of coal seams buried in the ground with a depth underone thousand meters. The process includes:

1. an overall development scheme in resource area is drawn up accordingto the amount of resources from coal resource exploration and the actualsituation of the geological formation;

2. the simultaneous development of a same layer of a single well ormultiple wells is implemented according to the overall scheme;

3. the development of several sets of coal seams is required to follow aprinciple of development from a deeper seam coal seam to a less deepercoal seam;

4. the pressure coefficient of coal seams needs to be greater than 0.9to ensure the economical implementation of the development scheme;

5. a well drilling process is utilized to establish a production well,that is, after drilling to the top of the deepest coal seam by utilizingthe well drilling process, a casing is put down for well cementation,and then a cement plug is drilled to open the coal seams;

6. a directional drilling process is utilized, a specific hydrauliccutting drill and specific double-layer tubular columns are used, fluidwith a certain performance is prepared, and production is performed by aground mud pump;

-   -   1) a directional drilling process is utilized, and a downhole        television set, a position finder and a direction instrument are        used to ensure the quality of tunneling;    -   2) for a specific hydraulic cutting drill, hydraulic cutting        drills of different parameters are customized according to        thicknesses and dip angles of the coal seams, and the parameters        mainly include rotation speed, the diameter of nozzles, and the        jet angle of nozzles;    -   3) for specific double-layer tubular columns, tubular columns of        different diameters are utilized according to capacity;    -   4) the performance of the fluid is configured according to the        pressure coefficient and density of coal seams, and the main        performance indexes include density, viscosity and cutting        force; the fluid (also called coal alkali liquor) is mainly        prepared from water, bentonite, caustic soda (sodium hydroxide),        coal powder and gangue powder;    -   5) the main parameters of a mud pump include pressure (generally        high pressure, which is greater than 10 MPa) and displacement;

7. mixture of coal briquettes and coal gas (CH4) is brought out of theground through fluid with a certain flow velocity and then enters aprocessing system on the ground;

-   -   1) the mixture of mud, coal and gas enters a three-phase        separation system first so that the mud, coal and gas are        separated simultaneously;    -   2) the coal gas (CH4) enters a gas processing station, is then        compressed and transmitted to users;    -   3) the coal briquettes enter a coal washing workshop and are        then processed into cleaned coal, which is transferred to a        cleaned coal warehouse for sale; ash and gangue from the coal        washing workshop enter a gangue grinding plant and are then        processed into materials below 200 meshes for preparing mud; and        waste water from the coal washing workshop is transferred to a        mud preparation plant and used for preparing mud; and    -   4) the mud flows into a sedimentation tank from the three-phase        separator for settling powdered coal and fine sand particles;        and the sediment is transferred to the coal washing workshop for        processing, and the mud is recycled to a circulation pool for        recycling.

According to the development scheme, a multi-well and multilayer wellpattern is implemented so as to perform the underground hydraulic miningof coal.

For a mining area having multiple coal seams, it is preferred to minebottom coal seams and then upper coal seams successively.

Embodiments of the present invention has the following advantages:

1. the synchronous mining of gas and solid of a coal field is realized,and the utilization ratio of resources is high; the recovery ratio ofcoal may be 80% and above; the gas is completely recycled;

2. downhole unmanned and hydraulic operations are realized, so as toavoid production accidents such as gas explosion, collapse and the likeduring conventional coal mining;

3. this novel process is more advantageous in terms of environmentalprotection than the conventional coal mining, is free of damages to theambient environment, and has small occupation of production land, nosewage discharge, no waste, gangue and dust; and, the coal gas is fullyrecycled;

4. stock resources in various places may be fully utilized, therebyavoiding the long-distance transportation of coal and reducing theenergy consumption;

5. less investment in construction, short cycle and high productionefficiency are realized; and

6. vigorous exploration and development of deep resources, mainly cokingcoal, may significantly make up the resource shortage and has goodbenefit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of flow of a process according to anembodiment of the present invention.

Reference numerals and corresponding explanation FIG. 1 are listed asbelow:

1 Electricity transformer and distributor 2 Power distribution cabinet 3Fluid circulating pump 4 Well winch 5 Derrick 6 Three-phase separator 7Natural gas processing station 8 Separated liquid phase 9 Separated coal10 Sedimentation tank 11 Sediment processing device 12 Fluid 13 Specifichydraulic mining drill 14 Inner tubular column 15 Outer tubular column16 Casing 17 Coal seams

FIG. 2 is a planar graph of flow of the process according to anembodiment of the present invention.

Reference numerals and corresponding explanation in FIG. 2 are listed asbelow:

1 Electricity transformer and distributor 2 Pump 3 Mud circulating pool4 Wellhead 5 Three-phase separator 6 Natural gas processing station 7Users 8 Sedimentation tank 9 Sediment processing device 10 Separatedliquid phase 11 Separated coal 12 Coal washing workshop 13 Cleaned coalwarehouse

DETAILED DESCRIPTION

The specific embodiments of the present invention will be furtherdescribed hereinafter with reference to the accompanying drawings.

Referring to FIG. 1, according to the well drilling process of anembodiment of the present invention, a system which includes anelectricity transformer and distributor (1), a power distributioncabinet (2), a mud circulating pump (3), a well winch (4) and a derrick(5) is utilized to perform drilling to the top of the deepest coal seam,a casing (16) is put down for well cementation, and then a cement plugis drilled to open the coal seams (17). The pressure coefficient of coalseams is required to be greater than 0.9 to ensure the economicalimplementation of the development scheme.

Referring to FIG. 1, a directional drilling process according to anembodiment of the present invention is utilized, the prepared fluid (12)with certain performance transmits hydraulic power to the coal seams fortunneling by a ground mud pump (3) via a specific double-layer tubularcolumn (i.e., an inner tubular column (14) and an outer tubular column(15)), and the coal deeply buried in the ground is washed and cut byusing a specific hydraulic cutting drill (13). The coal mixture isbrought out of the ground through fluid with a certain flow velocity andthen enters a ground processing system.

Referring to FIG. 1, the parameters of the mud pump (3) in an embodimentof the present invention mainly include pressure and displacement. Thepressure is required to be a high pressure, generally greater than 10MPa.

Referring to FIG. 1, for the specific double-layer tubular columns in anembodiment of the present invention, i.e., the inner tubular column (14)and an outer tubular column (15), the tubular columns (14, 15) ofdifferent diameters are utilized according to production capacity. Theperformance of the fluid (12) in an embodiment of the present inventionis configured according to the pressure coefficient and density of coalseams, and the main performance indexes include density, viscosity andcutting force.

Referring to FIG. 1, for a specific hydraulic cutting drill (13) in anembodiment of the present invention, hydraulic cutting drills (13) ofdifferent parameters are customized according to thicknesses and dipangles of the coal seams (17), and the main parameters include rotationspeed, the diameter of nozzles, and the jet angle of nozzles.

Referring to FIG. 1, the fluid (12) (also called coal alkali liquor) inan embodiment of the present invention is mainly prepared from water,bentonite, caustic soda (sodium hydroxide), coal powder and ganguepowder.

Referring to FIG. 2, a planar graph of flow of the process is shown,including an electricity transformer and distributor (1), a pump (2), amud circulating pool (3) and a wellhead (4). The coal mixture in anembodiment of the present invention enters a three-phase separationsystem (5) first so that the mud (10), coal (11) and gas (7) of threephases are separated, respectively.

Referring to FIG. 2, the coal gas (CH4) in an embodiment of the presentinvention enters a gas processing station (6), is then compressed andtransmitted to users.

Referring to FIG. 2, coal briquettes (11) in an embodiment of thepresent invention enter a coal washing workshop (12) and are thenprocessed into cleaned coal, and the cleaned coal is transferred acleaned coal warehouse (13) for marketing.

Referring to FIG. 2, the mud (10) in an embodiment of the presentinvention flows into a sedimentation tank (8) after separation, powderedcoal and fine sand particles are settled by a sediment processing device(9), the sediment is transferred to the coal washing workshop (12) forprocessing, and the mud is recycled to a circulation pool (3) forrecycling.

1-10. (canceled)
 11. A method for hydraulic mining and fluid carrying ofdeep-seam coal, for realizing a coal development with integration ofsynchronous mining of gas and solid of coal fields, for the coal seamswhich cannot be mined with a conventional method or are uneconomicallymined, and for the establishment of gasification tunnels of undergroundgasification of coal, wherein the method includes: by a directionaldrilling process, using a hydraulic cutting drill and double-layertubular columns, preparing and using fluid with a certain performance asa carrier, and bringing mixture of underground deep-seam coal out of theground through the fluid with a flow velocity; simultaneously separatingmud, coal and gas in the mixture by a three-phase separator system; andcoal gas being fed into a gas processing station, then being compressedand transmitted to users; coal briquettes entering a coal washingworkshop and being processed into cleaned coal, which is thentransferred to a cleaned coal warehouse for subsequent sale; and the mudbeing recycled to a circulation pool for recycling.
 12. The method forhydraulic mining and fluid carrying of deep-seam coal according to claim11, wherein an overall development scheme is drawn up according to theamount of resources from coal resource exploration and the actualsituation of the geological formation, and the simultaneous developmentof a same layer of a single well or multiple wells is implementedaccording to the overall scheme.
 13. The method for hydraulic mining andfluid carrying of deep-seam coal according to claim 11, wherein, severalsets of coal seams is developed from deep coal seam to shallow coalseam, and pressure coefficient of coal seams is greater than 0.9. 14.The method for hydraulic mining and fluid carrying of deep-seam coalaccording to claim 12, wherein, several sets of coal seams is developedfrom deep coal seam to shallow coal seam, and pressure coefficient ofcoal seams is greater than 0.9.
 15. The method for hydraulic mining andfluid carrying of deep-seam coal according to claim 11, wherein the welldrilling process is utilized to establish a production well; afterdrilling to the top of the deepest coal seam by the well drillingprocess, a casing is put down for well cementation, and then a cementplug is drilled to open the coal seams.
 16. The method for hydraulicmining and fluid carrying of deep-seam coal according to claim 11,wherein the directional drilling process is utilized, a specifichydraulic cutting drill and specific double-layer tubular columns areutilized, fluid with a certain performance is prepared, and finallyproduction is performed by a ground surface mud pump.
 17. The method forhydraulic mining and fluid carrying of deep-seam coal according to claim13, wherein the directional drilling process is utilized, a specifichydraulic cutting drill and specific double-layer tubular columns areutilized, fluid with a certain performance is prepared, and finallyproduction is performed by a ground surface mud pump.
 18. The method forhydraulic mining and fluid carrying of deep-seam coal according to claim15, wherein the directional drilling process is utilized, and a downholetelevision set, a position finder and a direction instrument are used toensure the quality of tunneling.
 19. The method for hydraulic mining andfluid carrying of deep-seam coal according to claim 16, wherein,hydraulic cutting drills of different parameters are customizedaccording to thicknesses and dip angles of the coal seams, and theparameters include rotation speed, the diameter of nozzles, and the jetangle of nozzles.
 20. The method for hydraulic mining and fluid carryingof deep-seam coal according to claim 16, wherein, the double-layertubular columns of different diameters are utilized according toproduction capacity, the performance of the fluid is configuredaccording to the pressure coefficient and density of coal seams, andindexes of the performance include density, viscosity and cutting force;the fluid is prepared from water, bentonite, caustic soda, coal powderand gangue powder; and parameters of the mud pump include pressure anddisplacement.
 21. The method for hydraulic mining and fluid carrying ofdeep-seam coal according to claim 11, wherein the mixture of coalbriquettes and coal gas is brought out of the ground through fluid witha certain flow velocity and then enters a processing system on theground.
 22. The method for hydraulic mining and fluid carrying ofdeep-seam coal according to claim 21, wherein the mixture of the fluidenters a three-phase separation system first so that the mud, coal andgas are separated simultaneously; the coal gas enters a gas processingstation, is then compressed and transmitted to users; the coalbriquettes enter a coal washing workshop and are then processed intocleaned coal, and the cleaned coal is transferred a cleaned coalwarehouse for subsequent sale; ash and gangue from the coal washingworkshop enter a gangue grinding plant and are then processed intomaterials below 200 meshes for preparing mud; waste water from the coalwashing workshop is transferred to a mud preparation plant and used forpreparing mud; the mud flows into a sedimentation tank from thethree-phase separator for settling powdered coal and fine sandparticles; and the sediment is transferred to the coal washing workshopfor processing, and the mud is recycled to a circulation pool forrecycling.